Valhalla 2300, Руководство по эксплуатации

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talker to indicate the end of a message.
SRQ - This wire may be asserted by any
device to indicate that it requires attention
(e.g. a fault has occurred or data is ready).
Usually the controller will respond by polling
the devices to determine which requires
service.
IFC - This wire is asserted by the controller to
reset the bus (note that only the bus is
affected) to an idle state.
REN - This wire is asserted by the controller
to indicate to all devices that they may enter
the REMOTE state. The user should note that
for a device to enter remote the REN wire
must be asserted and the device must
subsequently receive its listen address. If this
wire is not asserted then all devices will be in
the LOCAL state.
DAV - This wire is asserted by the talker and
indicates that a valid data byte has been
placed on the DIO0 to DIO7 wires.
NRFD - This wire may be asserted by any
listener and indicates that it is not yet ready to
receive further data.
NDAC - This wire may be asserted by any
listener and indicates that it has not yet
completed reading the data byte present on the
DIO wires.
7-4. Universal
Commands
This paragraph describes all of the IEEE-488
defined commands and their affect upon the
operation of the 2300. In this paragraph (as in
all further paragraphs) examples are given
using HP Basic and it is assumed that the
2300 has its listen address set to 15. If you are
using a programming language other than HP
Basic, consult your programmer's guide for
the correct command syntax.
7-4-1. Device Clear (DCL)
This command will cause all of the devices to
enter the reset state (both interface and
instrumental functions). The 2300 will
perform a power-on reset cycle when this
command is received. An example of this
command in HP Basic is
CLEAR 7 .
This command can sometimes cause the
interface to reset and then re-read the device
clear command if the responding instrument is
slow to release the handshake. This will be
visible as a complete bus lockout with all of
the devices continuously performing a device
clear. Although every precaution has been
taken to eliminate this problem with the
IEEE-488 Standard, lockout may sometimes
occur. It is recommended the Selective
Device Clear (SDC) Command be used where
possible.
7-4-2. Selective Device Clear (SDC)
This command will cause only the addressed
device to enter the reset state. This command
will perform the same function as the DCL
command of 7-4-1 but on individual
instruments only, thus overcoming the
problem inherent with the DCL command.
An example of this command in HP Basic is
CLEAR 715 which would reset only the
device at address 15.
7-4-3. Group Execute Trigger (GET)
The execution of this command is dependent
on the particular device receiving it, the exact
result not being defined by the IEEE-488
(1978) standard.
When received by the 2300 it will respond
with a handshake and will not cause an error
but will be ignored.
The user should note that only the
addressed form of this command is
defined by the IEEE 488 (1978)